Non-interference stress measurement systems (NSMSs) may be designed for collecting structural data associated with gas turbine engine components (e.g., using rotating airfoil vibration measurements correlated to airfoil stress). For example, the measured structural data may be used for engine design purposes, for engine certification processes, and/or for engine monitoring. NSMSs may utilize optical sensors to collect said structural data in engine components. Once collected, the structural data may be relayed to ground-based and/or in-flight electronics that process the data. Early NSMSs utilized large component cabinets located on the ground and linked to sensors on a test engine through fiber optic cable; however, current NSMSs have been designed with smaller components and may be integrated within the engine itself.
Further, in some circumstances it is desirable or necessary to collect in-flight engine structural data while an engine is mounted to an airframe. To implement NSMSs in-flight, improvements upon known NSMSs have been made to lessen the weight and mounting restrictions of previous models. Known NSMS implementations for collecting structural data about gas turbine engine components have been modified for use in-flight by using microcontrollers and smaller lasers mounted to components of the gas turbine engine. Known in-flight NSMSs can allow for automated NSMS data collection during operation, rather than the prior one-time, operator induced NSMS collection systems. Such examples are further detailed in U.S. Pat. No. 7,984,656 (“NSMS Flight Laser Detector System”).
When using an NSMS, the NSMS probes and NSMS probe configurations may not always provide accurate data. At times, the received data may be blurry, unclear, and/or imprecise; potential errors in calculations and analyses may be drawn from the blurry, unclear, and/or imprecise data. At times, the data may be so corrupted that it cannot be used at all.
One major cause of such data corruption may be the intensity of light that the optical fibers transmit and receive. Past designs may have used a collimated light setup, wherein optical transmit and receive fibers are positioned directly against the respective transmit and receive lenses. Such designs create an unfocused light beam down the center of the transmission lens; such unfocused light beams may cause reflections of unwanted light at various angles when the beam is directed at a target. A receiving lens in the NSMS sensor may receive such unwanted, reflected light, causing corruption in data derived from the reflected light. Because accuracy of the structural data collected by the NSMS is imperative, it can be seen that an improvement is needed to focus the light being transmitted from transmit fiber and optimize the reception apparatus for optimum light intensity for reception by receive sensors.